The present invention relates to a magnetic disk drive.
Thickness of a lubricant film applied onto a surface of magnetic disk is decreased on account of a centrifugal force and a shear force generated by rotation of the magnetic disk, and splashing by temperature rise in the magnetic disk drive. In order to maintain sliding durability between a magnetic disk and a magnetic head slider, a lubricant is supplied onto surface of the disk, or the lubricant is applied onto the surface of the disk. Various methods for supplying lubricants onto the surface of disk in a magnetic disk drive are disclosed in JPA-59-218668 (1984), JP-A-60-239921 (1985), JP-A-8-45238 (1996), JP-A-10-312660 (1998), JP-A-8-45239 (1996), JP-A-6-295579 (1994), Japanese Patent No. 2796852, and others.
In accordance with JP-A-59-218668 (1984), a lubricant is supplied onto the surface of magnetic disk from a venting hole at the center of the hub by generating the lubricant vapor from the lubricant impregnated member provided at the bottom of the device by heated air flow generated with rotation of the magnetic disk. In accordance with JP-A-60-239921 (1985), a lubricant film is formed on the surface of magnetic disk by depositing from myristic acid vapor, which is vaporized from a myristic acid impregnated member by blowing hot air thereon,. In accordance with JP-A-8-45238 (1996), a lubricant film made of a liquid lubricant is formed on an arm or a suspension, and the lubricant is supplied onto the surface of magnetic disk by an air flow accompanied with rotation of the magnetic disk. In accordance with JP-A-10-312660 (1998), JP-A-8-45239 (1996), and Japanese Patent No. 27906852, a liquid lubricant is supplied onto the surface of magnetic disk by placing a wick material, wherein the liquid lubricant having a low viscosity is impregnated, in the vicinity of the disk. In accordance with JP-A-6-295579 (1994), a lubricant is supplied from a reservoir provided with a heating element.
Thickness of lubricant film on the disk maintains a definite value under a condition that an amount of the lubricant reduced by scraping-off and splashing is balanced with an amount of the lubricant supplied by heat and air flow, and sliding durability between the magnetic disk and the magnetic head slider is ensured. However, if the balance is lost, the lubricating performance is lowered by continuous decrease of the lubricant film thickness, or reversely, too much increase of the lubricant film thickness. Furthermore, another cause for decreasing the sliding performance is contamination of the head slider with various contaminants which are brought into the device from both exterior and interior of the device.
In order to solve the problem mentioned above, by supplying a lubricant, physical properties of the lubricant such as molecular structure and molecular weight, and the amount of the lubricant held in the magnetic disk drive must be studied in detail before practical use of the lubricant. In accordance with the prior art mentioned above, optimization of supplying amount of the lubricant, physical properties of the lubricant such as molecular structure and molecular weight, and the amount of the lubricant held in the magnetic disk drive are not practically studied nor disclosed. Accordingly, stable supply of the lubricant by heat or air flow is impossible.
Furthermore, operation systems and structures of the magnetic disk drive must be considered. For instance, in accordance with a CSS (Contact Start Stop) system disclosed in JP-A-59-218668 (1984), a strong adsorption (stiction) is generated between the head slider and the magnetic disk, if the lubricant film thickness is increased, and a trouble such as difficulty in starting up of the magnetic disk and the like are generated. Therefore, a L/UL (Load/Unload) system can be deemed as desirable for supplying a lubricant.